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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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package org.hisp.dhis.analytics;

import java.util.List;
import org.hisp.dhis.common.IllegalQueryException;

/**
 * Service interface which provides methods for validating and planning analytics queries.
 *
 * @author Lars Helge Overland
 */
public interface QueryPlanner {
  /**
   * Creates a DataQueryGroups object. It is mandatory to group the queries by the following
   * criteria: 1) partition / year 2) organisation unit level 3) period type 4) aggregation type.
   * The DataQueryGroups contains groups of queries. The query groups should be run in sequence
   * while the queries within each group should be run in parallel for optimal performance.
   * Currently queries with different {@link AnalyticsAggregationType} are run in sequence.
   *
   * <p>If the number of queries produced by this grouping is equal or larger than the number of
   * optimal queries, those queries are returned. If not it will split on the data element
   * dimension, data set dimension and organisation unit dimension, and return immediately after
   * each step if optimal queries are met.
   *
   * <p>It does not attempt to split on period dimension as splitting on columns with low
   * cardinality typically does not improve performance.
   *
   * @param params the data query parameters.
   * @param plannerParams the query planner parameters.
   * @return a {@link DataQueryGroups} object.
   */
  DataQueryGroups planQuery(DataQueryParams params, QueryPlannerParams plannerParams)
      throws IllegalQueryException;

  /**
   * Sets the table name and partitions on the given query.
   *
   * @param params the data query parameters.
   * @param plannerParams the query planner parameters.
   * @return a data query parameters.
   */
  DataQueryParams withTableNameAndPartitions(
      DataQueryParams params, QueryPlannerParams plannerParams);

  /**
   * Sets partitions on the given query
   *
   * @param params the data query parameters
   * @return a data query parameters
   */
  DataQueryParams assignPartitionsFromQueryPeriods(
      DataQueryParams params, AnalyticsTableType tableType);

  /**
   * If organisation units appear as dimensions; groups the given query into sub queries based on
   * the level of the organisation units. Sets the organisation unit level on each query. If
   * organisation units appear as filter; replaces the organisation unit filter with one filter for
   * each level. Sets the dimension names and filter names respectively.
   *
   * @param params the data query parameters.
   * @return a list of data query parameters.
   */
  List<DataQueryParams> groupByOrgUnitLevel(DataQueryParams params);

  /**
   * If periods appear as dimensions in the given query; groups the query into sub queries based on
   * the period type of the periods. Sets the period type name on each query. If periods appear as
   * filters; replaces the period filter with one filter for each period type. Sets the dimension
   * names and filter names respectively.
   *
   * @param params the data query parameters.
   * @return a list of data query parameters.
   */
  List<DataQueryParams> groupByPeriodType(DataQueryParams params);

  /**
   * If periods appear as dimensions in the given query; groups the given query into sub queries
   * based on start and end dates, i.e. one query per period. Marks the period dimension as fixed
   * and sets the dimension name to the period ISO name. Sets the start date and end date
   * properties. If periods appear as filters in the given query; sets the start date and end date
   * properties based on the first period and removes the period dimension.
   *
   * @param params the data query parameters.
   * @return a list of data query parameters.
   */
  List<DataQueryParams> groupByStartEndDateRestriction(DataQueryParams params);
}
